I'd go with one of the newer Prescott boards that supports RAID 1/1.5/2 and also has on board SATA. Obviously yer gonna want one with an 800 mHz FSB and allows for HT processing with four DIMM slots for RAM with a 2 gig capacity. Some of the boards have gigabit ethernet built in and that's a big plus for when higher speed networking gets introduced mainstream. Some of the boards also inclue Dolby Digital 5.1/6.1 digital cards with on board controllers which is also a nice feature.
Snag a board with all of those features and yer looking at $250 and you would be KING.